This invention relates to a mattress to be set on a bed frame.
A mattress is usually put on the bed frame and thus placed above the floor. Since the top of the mattress is flat and smooth, a user sleeping on it may fall onto the floor and may be injured. A known mattress has no means for preventing the user from falling. The user cannot help but be careful not to fall from the mattress. He must lie on the central part of the mattress, thus leaving the outer margins of the mattress unoccupied almost all the time he is sleeping.